Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
  • B22D11/005—Continuous casting of metals, i.e. casting in indefinite lengths of wire
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
  • B21C1/00—Manufacture of metal sheets, metal wire, metal rods, metal tubes by drawing
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
  • C03B37/01—Manufacture of glass fibres or filaments
  • C03B37/02—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor
  • C03B37/025—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor from reheated softened tubes, rods, fibres or filaments, e.g. drawing fibres from preforms
  • C03B37/026—Drawing fibres reinforced with a metal wire or with other non-glass material

Definitions

• This invention relates to the production of glass-insulated microwire with amorphous or microcrystalline microstructure.
• a method for casting microwires in glass insulation is disclosed in
• the electrical resistance of the amorphous wires increases from 160 K ⁇ m up to 2500 K ⁇ /m, and it becomes possible to obtain both positive and negative thermal coefficient of resistance.
• the initial magnetic permeability increase 5-7 times, and can reach 20x103.
• the mechanical strength of these amorphous microwires increases.
• Microcrystalline and amorphous microwires are well suited for applications such as sensors of temperature, static and dynamic pressure, velocity and liquid or gas consumption. It is the object of the present invention to prepare amorphous or micro ⁇ ystalline glass-insulated microwires.
• a glass-coated microwire with an amorphous metal core is prepared by providing a glass tube containing the desired metal and melting the metal in a high frequency induction field. The heat of the metal softens the glass tube and a thin capillary is drawn from the softened glass tube. If the metal wets the glass surface, a metal- filled capillary tube results. The rate of cooling is controlled such that an amorphous microstructure is obtained for the metal.
• a glass-coated microwire with a microcrystalline metal core is prepared by providing a glass tube containing the desired metal and melting the metal in a high frequency induction field and further heating the melted metal so that it becomes super heated.
• the heat of the metal softens the glass tube and a thin capillary is drawn from the softened glass tube. If the metal wets the glass surface, a metal-filled capillary tube results.
• the metal-filled capillary enters a cooling zone in a superheated state where it is rapidly cooled such that the desired amorphous or microcrystalline microstructure is obtained. Rapid cooling is typically required to obtain amorphous and imcrocrystalline microstructures.
• the rate of cooling is not less than 10 4 o C/sec and preferably is 10 5 -10 6 °C/sec.
• the amorphous or microcrystalline structure is controlled by choice of amorphisizers, cooling rate, nature of the cooling liquid, location of the cooling stream, dwell time in the cooling stream and degree of superheating and supercooling.
• Another aspect of the invention is a glass-coated microwire with a metal core having either a microcrystalline or amorphous microstructure prepared according to the method of the invention.
• FIG. 1 shows a diagram of the apparatus used in the practice of this invention.
• Figure 2 is a photograph to scale showing microwire prepared according to the method of the invention.
• the present invention as herein described relates to a method for preparing microcrystalline and amorphous glass-insulated microwires.
• Patent No. 3,256,584. The present invention is distinguished from the art in that means for controlling the microstructure of the wire disclosed.
• a method of producing amorphous and microcrystalline microwires using an apparatus 10 is described.
• a glass tube 11 is charged with a metal 12 and the tip of the tube 11 is introduced into the field of an induction coil 13.
• a heating zone 14 contains the glass tube 11, metal 12 and the high frequency induction coil 13.
• the high frequency coil 13 melts and superheats the metal 12 in tube 11.
• the heat generated softens the tip of the glass tube 11.
• a glass capillary 15 is drawn from the softened glass. If the metal can wet the surface of the glass, the capillary 15 is filled with metal.
• the capillary exits the heating zone 14 and enters the cooling zone 16 which contains a cooling hquid 17.
• the metal filled capillary 15 enters into a stream 18 of cooling liquid 17
• FIG. 1 is a photograph to scale showing the microwire prepared according to the method of the invention. Rapid cooling is typically required to obtain amorphous and microcrystalUne microstructures. The rate of cooling is not less than 10 4 °C/sec, and preferably is 10 5 -10 6 °C/sec. The amorphous or microcrystalline structure is controlled by choice of amorphisizers, cooling rate, nature of the cooling liquid, location of the cooling stream, dwell time in the cooling stream and degree of superheating and supercooling.
• the metal 12 is superheated while in the glass tube 11 in the high frequency induction field.
• the metal is superheated to preferably 100-400° C, and more preferably to 250-350° C, above its liquidus temperature Tii qu i dus - Heating the metal 12 above Tji quidus results in a steeper cooling curve and promotes amorphization of the metal.
• Supercooling occurs when the superheated metal-filled capillary 15 enters a stream of cooling liquid 17 in the cooling zone 16.
• Amorphous structure will exist when the rate of crystal growth, v 2 is less than the rate of heat loss, ⁇ 2 - When v, « v 2 , the metal will supercool and this promotes the formation of the amorphous structure.
• the extent of cooling is controlled in part by the path length 21 of the cooling of liquid 17.
• the cooling stream 18 has a variable path length and is preferably greater than 3 mm long and more preferably 5-7 mm long.
• the cooling hquid can be any Hquid, but is preferably water, transformer oil, silicon organic liquids, and hquid nitrogen.
• the cooling zone 16 is variably positioned a distance from the heating zone 14. The distance influences the degree to which the metal- filled capillary 15 is superheated. The further the distance between the two zones, the greater the heat loss before entering the cooling zone.
• the cooling zone 16 is preferably less than 100 mm, and more preferably 40-50 mm, from the heating zone.
• the microwire 19 sohdifies in the cooling zone and upon exiting, is supercooled at least 20° C below its melting temperature, T HqUjdus . Preferably, the microwire is supercooled 40-60° C below
• the dwell time of the microwire in the cooling zone 16 is adjusted so as to promote the amorphous or rmcrocrystalline microstructure in the wire. Sufficient time in the cooling zone is required to completely cool the wire below Tu ⁇ .
• the microwire is preferably drawn at a speed of preferably not less than 150 m/rnin, and more preferably 300-500 m/min, through the cooling zone.
• the composition of the metal is controlled so as to promote amorphization.
• Metals used in the practice of the invention are any metal, particularly any transition metal or Group Ilia or r a metal and their alloys. Additives are used with the above metal to promote amorphization. Possible additives include phosphorous, boron, silicon, zinc and rare earth metals which are added to the metal preferably in the range of 3 to 10 wt%, and more preferably 6 to 8 wt%.
• the diameter of the microwire influences the final microstructure because the rate of heat loss, v 2 , changes with diameter.
• Microwires greater than 40 ⁇ m in diameter are usually rmcroCTyst ⁇ lline.
• Microwires less than 10 ⁇ m are usually amorphous.
• Microwires in the range of 40 to 10 ⁇ m will have a microstructure strongly influenced by the processing parameters. For example, increasing the additive load in the metal, lengthening the cooling stream path length, reducing the distance between the cooling and heating zones and increasing the degree of superheating and supercooling of the metal all promote an amorphous microstructure in a 20 ⁇ m diameter wire.
• the glass coating solidifies before the metal core as the wire passes through the cooling zone.
• the metallic core is in a strained state of extension and the glass coating is in a state of compression.
• the strain is induced by the differences in the coefficients of thermal expansion of glass and metal.
• the molten metal tries to contract on coohng but is constrained by the already solidified glass. Resistance, mechanical strength and magnetic properties actually benefit from this situation.
• a glass tube used in the preparation of microwires had the following dimensions: inner diameter of 5-15 mm, preferably 9-12 mm; wall thickness of 0.8-2 mm, preferable 1-1.2 mm.
• the glass must be of a very high purity to prevent hairline cracks and have a melting point comparable to the melting point of the metal used in the experiment.
• a Ni-Cr-Si-Ce alloy were added to a glass tube with the dimensions described above.
• the alloy had a T Uquidus of 1320° C.
• the metal was heated in a high field inductor to 260-280° C above T bquidus , that is to 1600° C.
• a capillary tube was drawn from the heating zone at a rate of 750 m/min.
• the cooling zone was positioned 10 mm from the heat zone.
• the coohng liquid was water. Liquid nitrogen as the cooling hquid was also used, however, no change in the microstructural properties of the wire were noted.
• the width of the coohng stream was 5 mm.
• the metal was supercooled 32-38° C.
• the resulting microwire was amorphous in structure and had a diameter of 3-5 ⁇ 12% ⁇ m.
• a 0.5 ⁇ m thick amorphous wire prepared according to the method of the invention had a resistance of 2.5 M ⁇ /m by the practice of this invention.
• a 20 ⁇ m thick crystalline microwire has a resistance of 150 K ⁇ /m.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Geochemistry & Mineralogy (AREA)
• Manufacturing & Machinery (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Soft Magnetic Materials (AREA)
• Powder Metallurgy (AREA)
• Glass Compositions (AREA)

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• 1991
  • 1991-09-26 US US07/766,034 patent/US5240066A/en not_active Expired - Fee Related
• 1992
  • 1992-09-01 CA CA002119894A patent/CA2119894A1/fr not_active Abandoned
  • 1992-09-01 WO PCT/US1992/007351 patent/WO1993005904A2/fr not_active Application Discontinuation
  • 1992-09-01 JP JP5506061A patent/JPH08503891A/ja active Pending
  • 1992-09-01 EP EP92920257A patent/EP0651681A1/fr not_active Withdrawn

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